He alleges he was ordered to do so in mid-2013 by then Garda Commissioner Martin Callinan and with the knowledge of then Deputy Commissioner Noirin O’Sullivan. They both deny his allegations.

While Sgt McCabe was investigated over an allegation made by a woman known as Ms D, the DPP decided in 2007 there should be no charges and what was described in the complaint did not amount to a crime.

Today, Mr Williams told Diarmaid McGuinness SC, for the tribunal, that he was “surprised” when he was named in the Dail by Joan Collins TD as having had penalty points quashed by the gardai.

“I didn’t know it was coming,” he said, adding: “I was surprised but I had nothing to hide.”

He had no evidence to associate the leak with Sgt McCabe and did not equate deputy Collins with either garda whistleblower.

“I had nothing to hide, I didn’t do anything wrong, if it was out there in the public domain, so what?” he said.

Apart from “vague, general rumours”, he had heard nothing specific about Sgt McCabe until he went to Ms D’s house in 2014 and her family told him about the allegation, he said.

“There was a rumour out there that he may have had a grievance with his own authorities, that he had fallen out with them, it was very very vague,” Mr Williams said.

He had not been briefed by anyone in the gardai and did not hear it from Supt Taylor.

Mr Williams said Mr D had got in contact and said Ms D wanted to talk to him after she had been visited by two journalists.

Mr McGuinness then took him through his phone records, showing contact with Ms D and her family in March 2013.

“My understanding is the reason she talked to me is that she was quite disconcerted that journalists had called to her home unsolicited, knew her name, knew her address, knew that she had made an allegation and as a result of that she wanted to speak out about it,” Mr Williams said.

He did not know what she wanted to talk about until he met her on March 8. He had spoken to her parents and they consented to the interview being video recorded.

Mr Williams denied that he called Supt Taylor from Ms D’s house that day and said “guess where I am now.”

There was a record of a call to Supt Taylor’s phone on March 7 and Mr Williams said he did recall this and it was about a separate story.

He said he never told Supt Taylor he was going to interview Ms D as it was “none of his business.”

Records showed the next working day, March 10, he said, he called Supt Taylor. Mr McGuinness said the record “seemed to support” Mr Williams’s evidence.

Mr Williams said he asked Supt Taylor if the investigation Ms D told him about had taken place as he needed to check it.

He did not recall how quickly Supt Taylor got back with the information. Mr D had told him that the incident was not recorded on the garda Pulse system - he put this to Supt Taylor, who confirmed it, he said.

Mr McGuinness asked him about phone conversations he had with then-assistant Garda Commissioner Norin O’Sullivan in late February 2014.

Mr Williams said this was about personal security issues and he had no discussions with her about Sgt McCabe.

Mr McGuinness asked him if he would not consider the confirmation of details of a sexual assault allegation against a serving garda to be part of a smear campaign.

Mr Williams replied that he did not, adding: “I ask questions for a living and people answer them.”

He said he did not approach Sgt McCabe to get his side of the story because he was not going to be identified in the articles.

Mr McGuinness said it was made public that Mr Williams and others had penalty points quashed and “it seems odd” that he would go up to Ms D’s house.

Mr Williams replied that “was not the reason why I went up there.”

Following his request after the interview, Supt Taylor had confirmed to him that there had been an investigation, a file had been sent to the DPP and it was decided there would be no prosecution, he said.

He told Supt Taylor about his interview with Ms D but “kept it very straight.”

“If Mr Taylor negatively briefed me… I would tell you, and I would also tell you if Noirin O’Sullivan had given me that information,” Mr Williams said. “Because they have given waivers, I don’t have anything to hide in relation to these people.”

He said calls he made to Supt Taylor on the eve of publication of the first article were “last minute queries.”

Tribunal Chairman Peter Charleton said Supt Taylor’s evidence had been that there was “one phone call” by Mr Williams in which he said he was going to write an article about “Maurice McCabe destroying this young girl’s life.”

John Ferry BL, for Supt Taylor, put this to Mr Williams, and that Supt Taylor had “previous communications over a period of time” with Mr Williams, who was one of the people he negatively briefed about Sgt McCabe.

Mr Williams denied this. Supt Taylor said the briefing happened in the course of different conversations from the middle of 2013 onward.

Mr Williams said he was confused as to what Supt Taylor was saying. He was “loathe” to access his phone records but he did so because of Supt Taylor’s evidence.

Mr Ferry said Supt Taylor had said his negative briefing consisted of opportunistically “dropping it into conversation” and he did this on a number of occasions prior to Mr Williams going to Ms D’s house.

“That is incorrect,” Mr Williams replied.

He said in the “whole narrative around this” there was an implication that he was part of a smear campaign and he got “eviscerated” on social media.

“I had no prior discussion about this at all with Dave Taylor,” he said.

Mr Ferry said Mr Taylor said he did not know Mr Williams was going to Ms D’s house before he phoned and said “guess where I am.”

“I never had that conversation with Mr Taylor,” Mr Williams reiterated.

Mr Charleton said Mr Ferry was suggesting that the reason the alleged call was in “that format” was because Supt Taylor “previously briefed you about the allegation.”

“That is incorrect,” Mr Williams replied.

He added that he agreed Mr Taylor did not “direct him down there.”

Supt Taylor had said there were “various conversational pieces” with Mr Williams in 2013 “around Sgt McCabe.”

Mr Taylor said he would have had no need to answer queries about the case after the interview because he had already briefed Mr Williams, Mr Ferry said.

“He never briefed me, he never discussed Maurice McCabe with me until I phoned him after I had interviewed Ms D,” Mr Williams replied.